Bovine Pancreatic Polypeptide Research Articles

Pancreatic Polypeptide Administration Enhances Insulin Sensitivity and Reduces the Insulin Requirement of Patients on Insulin Pump Therapy

The effects of pancreatic polypeptide (PP) infusion were examined in patients on insulin pump therapy to determine whether PP administration can reduce insulin requirements in patients with type 1 diabetes mellitus (T1DM) or type 3c diabetes mellitus (T3cDM; pancreatogenic). Ten subjects with long-standing T1DM (n = 7) or T3cDM (n = 3) on insulin pump treatment received a 72 h subcutaneous infusion of 2 pmol/kg/min bovine PP or saline by portable infusion pump in a single-blinded, randomized, crossover design. Pancreatic polypeptide infusion raised plasma PP levels to 450-700 pmol/liter. Daily insulin infusion requirements (I) fell from 48 ± 6.9 to 40 ± 7.5 U on day 2 (p < .05) and from 46 ± 7.7 to 37 ± 6.6 U on day 3 (p < .05) of PP infusion compared with saline. Corrected for average blood glucose concentration (G), I/G fell in 10/10 subjects during the second 24 h period and in 7/10 subjects during the third 24 h period; sensitivity to insulin, calculated as 1/(I/G), increased 45% ± 12% on day 2 (p < .01) and 34% ± 14% on day 3 (p < .05) of PP infusion. Pancreatic polypeptide responses to a test meal were compared with the change in insulin infusion requirements in 5 subjects; the reduction in insulin requirements seen during PP infusion correlated with the degree of baseline PP deficiency (p < .002). A concurrent subcutaneous infusion of PP enhances insulin sensitivity and reduces insulin requirements in patients with long-standing T1DM and T3cDM on insulin pump therapy. The benefit of PP infusion correlated with the degree of PP deficiency.

Changes in blood pancreatic polypeptide and ghrelin concentrations in response to feeding in sheep1

The roles of pancreatic polypeptide (PP) have not been determined in ruminant animals. The aim of the present study was to examine the role of PP in the regulation of ghrelin secretion in sheep. Two experiments were conducted using four 2-yr-old Suffolk wethers fed a maintenance diet of alfalfa hay cubes. In Exp. 1, the effects of feeding on blood ghrelin and PP concentrations were examined in scheduled-fed sheep. Blood samples were collected every 10 min from 30 min before to 360 min after feeding. Plasma PP concentrations were transiently increased from the preprandial average value to the values from 30 to 60 min after feeding and gradually decreased (P < 0.05) to stable values from 150 to 180 min. The values from 30 to 60 min were greater (P < 0.05) than those from 150 to 360 min. In contrast, plasma ghrelin concentrations were gradually decreased (P < 0.01) by feeding. The values from 60 to 360 min were less (P < 0.01) than the preprandial average value. In Exp. 2, the effects of continuous PP infusion on ghrelin secretion were examined in feed-deprived sheep. The animals were deprived of feed for 48 h before PP infusion. The PP-treated group intravenously received synthetic bovine PP at a rate of 10 pmol.kg(-1 )of BW.min(-1) for 180 min. Blood samples were collected every 10 min from 30 min before to 180 min after the commencement of PP infusion. Plasma PP concentrations reached a plateau within 30 min after the commencement of PP infusion. Plasma ghrelin concentrations were decreased (P = 0.002, 0.016, 0.007) by PP infusion at 160, 170, and 180 min, respectively. In conclusion, plasma ghrelin and PP concentrations were decreased and increased, respectively, in response to feeding in ruminant animals. Furthermore, PP could depress ghrelin secretion.

An immunohistochemical study of endocrine cells in the pancreas of the Red-bellied frog (Bombina orientalis)

The regional distribution and frequency of pancreatic endocrine cells in the red-bellied frog, Bombina orientalis, were studied by the immunohistochemical peroxidase anti-peroxidase (PAP) method using five types of specific mammalian antisera to insulin, glucagon, somatostatin, bovine pancreatic polypeptide (PP) and secretin. The frequency was calculated as the mean number of each endocrine cell type/1,000 total cells (including exocrine and endocrine cells) using an automated image analysis process. The percentage of each immunoreactive (IR) cell species to the total IR cell population was also calculated. In the pancreas of the red-bellied frog, all five endocrine cell types were demonstrated. Insulin IR cells were located in the pancreas as single cells or islet-like clusters. The latter were localized in central regions. The insulin-IR cells showed a frequency of 65.40 plus/minus 14.56/1,000 cells. Glucagon IR cells were also detected as single cells or as clusters but in the case of clusters, two distributional patterns were detected - a central core type and a marginally distributed type. They showed an abundance of 32.70 plus/minus 7.32/1,000 cells. Somatostatin-IR cells were dispersed throughout the pancreatic parenchyma as single cells, three to four cells, or clusters. The clusters were located in the marginal regions. The somatostatin-IR cell frequency was 19.40 plus/minus 6.52/1000 cells. PP-IR cells were randomly distributed throughout the pancreatic parenchyma as single cells with a frequency of 14.70 plus/minus 4.92/1,000 cells. Secretin-IR cells were demonstrated as clusters or as single cells, and as clusters they occupied the central regions. They showed a frequency of 39.60 plus/minus 10.36/1,000 cells. This is the first report of the presence of secretin-IR cells in amphibian pancreatic endocrine cells. Overall, there were 37.20 plus/minus 6.84% insulin-, 21.90 plus/minus 5.55% glucagon-, 11.60 plus/minus 4.33% somatostatin-, 8.60 plus/minus 2.72% PP- and 23.40 plus/minus 4.45% secretin-IR cells.

Enantioselective Artificial Metalloenzymes Based on a Bovine Pancreatic Polypeptide Scaffold

Site creation: Enantioselective artificial metalloenzymes have been created by grafting a new active site onto bovine pancreatic polypeptide through the introduction of an amino acid capable of coordinating a copper(II) ion. This hybrid catalyst gave good enantioselectivities in the Diels-Alder and Michael addition reactions in water (see scheme) and displayed a very high substrate selectivity.

Enantioselective Artificial Metalloenzymes Based on a Bovine Pancreatic Polypeptide Scaffold

AbstractKunstvolles Design: Enantioselektive künstliche Metalloenzyme wurden erzeugt, indem eine zur Koordination von Kupfer(II)‐Ionen befähigte Aminosäure als neues aktives Zentrum in bovines pankreatisches Polypeptid (bPP) eingeführt wurde. Der Hybridkatalysator liefert gute Enantioselektivitäten in Diels‐Alder‐ und Michael‐Reaktionen in Wasser (siehe Schema) und zeigt eine sehr hohe Substratselektivität.magnified image

Backbone thioester exchange: a new approach to evaluating higher order structural stability in polypeptides.

An amide bond has been replaced by a thioester in bovine pancreatic polypeptide (bPP) to allow rapid and reversible (dynamic) exchange of the alpha-helical segment with other thiols in solution. We have begun to study the higher order structural stability of bPP by measuring the equilibrium constant of the "backbone thioester exchange" (BTE) reaction. The extent to which the equilibrium (KBTE) favors one set of peptides over the other, which can be easily measured, can be directly correlated to the energy gained from favorable noncovalent interactions that occur between peptide segments on either side of the thioester bond (Kfold).

An immunohistochemical study of the gastrointestinal endocrine cells in the ddY mice

The distributions and frequencies of some endocrine cells in the gastrointestinal (GI) tract of ddY mice were studied with immunohistochemical method using 7 types of antisera against bovine chromogranin (BCG), serotonin, gastrin, cholecystokinin (CCK)-8, somatostatin, glucagon and human pancreatic polypeptide (HPP). All of 7 types of immunoreactive (IR) cells were identified. Most of IR cells in the intestinal portion were generally spherical or spindle in shape (open typed cell) while cells showing round in shape (close typed cell) were found in the intestinal gland and stomach regions occasionally. Their relative frequencies were varied according to each portion of GI tract. BCG-IR cells were demonstrated throughout whole GI tract except for the cecum and they were most predominant in the fundus and pylorus. Serotonin-IR cells were detected throughout whole GI tract and they were most predominant cell types in this species of mice. Gastrin-IR cells were restricted to the pylorus and CCK-8-IR cells were demonstrated in the pylorus, duodenum and jejunum with numerous frequencies in the pylorus. Somatostatin-IR cells were detected throughout whole GI tract except for the cecum and rectum and they showed more numerous frequencies in the stomach regions. In addition, glucagon-IR cells were restricted to the fundus, duodenum and jejunum with rare frequencies, and HPP-IR cells were restricted to the rectum only with rare frequency. In conclusion, some strain-dependent unique distributional patterns of gastrointestinal endocrine cells were found in GI tract of ddY mice.

Nucleophilic and general acid catalysis at physiological pH by a designed miniature esterase.

A 31-residue peptide (Art-Est) was designed to catalyse the hydrolysis of p-nitrophenyl esters through histidine catalysis on the solvent exposed face of the alpha-helix of bovine pancreatic polypeptide. NMR spectroscopy indicated that Art-Est adopted a stable 3-dimensional structure in solution. Art-Est was an efficient catalyst with second order rate constants of up to 0.050 M(-1) s(-1). The activity of Art-Est was a consequence of the increased nucleophilicity of His-22, which had a reduced pK(a) value of 5.5 as a consequence of its interaction with His-18 and the positively charged Arg-25 and Arg-26. Mass spectrometry and NMR spectroscopy confirmed that the Art-Est catalysed hydrolysis of p-nitrophenyl esters proceeded through an acyl-enzyme intermediate. A solvent kinetic isotope effect of 1.8 indicated that the transition state preceding the acyl intermediate was stabilised through interaction with the protonated side-chain of His-18 and indicated a reaction mechanism similar to that generally observed for natural esterases. The involvement in the reaction of two histidine residues with different pK(a) values led to a bell-shaped dependence of the reaction rate on the pH of the solution. The catalytic behaviour of Art-Est indicated that designed miniature enzymes can act in a transparent mechanism based fashion with enzyme-like behaviour through the interplay of several amino acid residues.

In vitro and in vivo characterization of 3-[2-[6-(2-tert-butoxyethoxy)pyridin-3-yl]-1H-imidazol-4-yl]benzonitrile hydrochloride salt, a potent and selective NPY5 receptor antagonist.

To investigate the anorectic potential of NPY5 receptor antagonists, we have profiled the in vitro and in vivo properties of 3-[2-[6-(2-tert-butoxyethoxy)pyridin-3-yl]-1H-imidazol-4-yl]benzonitrile hydrochloride salt (1). This compound was found to have excellent NPY5 receptor affinity and selectivity, potent functional antagonism, and good peripheral and central nervous system exposure in rats. This compound attenuated bovine pancreatic polypeptide induced food intake in rats but failed to demonstrate anorectic activity in rodent natural feeding models.

Design and Synthesis of the Potent, Orally Available, Brain-Penetrable Arylpyrazole Class of Neuropeptide Y5 Receptor Antagonists

Novel arylpyrazole derivatives were synthesized and evaluated as neuropeptide Y (NPY) Y5 receptor antagonists. Compound (-)-7, which features a novel chiral 2,3-dihydro-1H-cyclopenta[a]naphthalene moiety, showed good binding affinity and antagonistic activity for the Y5 receptor. After intracerebroventricular administration in SD rats, (-)-7 significantly inhibited food intake that was induced by the centrally administered Y5-preferring agonist, bovine pancreatic polypeptide, but had only a negligible effect on NPY-induced feeding.

Bovine pancreatic polypeptide (bPP) undergoes significant changes in conformation and dynamics upon binding to DPC micelles.

The pancreatic polypeptide (PP), a 36-residue, C-terminally amidated polypeptide hormone is a member of the neuropeptide Y (NPY) family. Here, we have studied the structure and dynamics of bovine pancreatic polypeptide (bPP) when bound to DPC-micelles as a membrane-mimicking model as well as the dynamics of bPP in solution. The comparison of structure and dynamics of bPP in both states reveals remarkable differences. The overall correlation time of 5.08ns derived from the 15N relaxation data proves unambiguously that bPP in solution exists as a dimer. Therein, intermolecular as well as intramolecular hydrophobic interactions from residues of both the amphiphilic helix and of the back-folded N terminus contribute to the stability of the PP fold. The overall rigidity is well-reflected in positive values for the heteronuclear NOE for residues 4-34. The membrane-bound species displays a partitioning into a more flexible N-terminal region and a well-defined alpha-helical region comprising residues 17-31. The average RMSD value for residues 17-31 is 0.22(+/-0.09)A. The flexibility of the N terminus is compatible with negative values of the heteronuclear NOE observed for the N-terminal residues 4-12 and low values of the generalized order parameter S(2). The membrane-peptide interface was investigated by micelle-integrating spin-labels and H,2H exchange measurements. It is formed by those residues which make contacts between the C-terminal alpha-helix and the polyproline helix. In contrast to pNPY, also residues from the N terminus display spatial proximity to the membrane interface. Furthermore, the orientation of the C terminus, that presumably contains residues involved in receptor binding, is different in the two environments. We speculate that this pre-positioning of residues could be an important requirement for receptor activation. Moreover, we doubt that the PP fold is of functional relevance for binding at the Y(4) receptor.

Design of a folded, conformationally stable oxaloacetate decarboxylase

Oxaldie-4, a 31-residue polypeptide designed to catalyse the decarboxylation of oxaloacetate, has been synthesised and its structural and catalytic properties characterised. The solution structure of Oxaldie-4 was studied by CD and NMR spectroscopy. Oxaldie-4, the design of which was based on bovine pancreatic polypeptide, adopted a stably folded structure in solution, which was characterised by the tight packing of a poly-proline-like helix and an α-helix as shown by a large number of inter-helix NOEs. The structure of Oxaldie-4 was in sharp contrast to the molten globule-like structure formed by Oxaldie-3, which was based on avian pancreatic polypeptide. The stability of Oxaldie-4 with respect to thermal and urea denaturation was significantly improved when compared to Oxaldie-3. Oxaldie-4 catalysed the decarboxylation of oxaloacetate with Michaelis-Menten saturation kinetics. The kinetic parameters, which were independent of the concentration of the catalyst over the whole range studied, were determined in a spectrophotometric assay at pH 7 and 298 K to be 0.229 s−1, 64.8 mM, and 2.9 M−1 s−1 for kcat, KM, and kcat/KM, respectively. This catalytic efficiency corresponds to a rate increase of almost four orders of magnitude when compared to simple amines such as butylamine. However, despite the stable three-dimensional structure, the catalytic efficiency of Oxaldie-4 was only slightly improved relative to Oxaldie-3, most likely the consequence of the high flexibility of the lysine side chains, which make up the active site of Oxaldie-4.

Immunohistochemical study of the distribution of endocrine cells in the gastrointestinal tract of the camel (Camelus bactrianus).

The regional distribution and relative frequency of endocrine cells in the gastrointestinal tract of the camel, Camelus bactrianus, were investigated using immunohistochemical methods. Ten types of immunoreactive (IR) endocrine cells were identified in this study. Among these cell types, only serotonin- and somatostatin-IR cells were detected in almost all regions of the gastrointestinal tract. Most of the cell types showed peak density in the pyloric gland region. The others showed restricted distribution: gastrin, cholecystokinin (CCK), motilin, bovine pancreatic polypeptide (BPP), and (gastric) substance P in the stomach; gastrin, CCK, BPP, gastric inhibitory polypeptide (GIP), glucagon, peptide tyrosine tyrosine (PYY) and substance P in the small intestine; and CCK, motilin, BPP, and PYY in the large intestine. Fundamentally the distribution pattern of endocrine cells in the gastrointestinal tract of the camel is similar to that of cattle. The distribution and frequency of endocrine cells in the glandular sac region are the same as those of the cardiac gland.

Comparative study of endocrine cells in the principal pancreatic islets of two teleosts, Silurus asotus (Siluridae) and Siniperca scherzeri (Centropomidae)

The regional distribution and relative frequency of some endocrine cells in the principal pancreatic islets of two teleosts, Silurus asotus Linne (Siluridae) and Siniperca scherzeri Steindachner (Centropomidae), which have similar feeding habits, were observed using specific antisera against insulin, glucagon, somatostatin and bovine pancreatic polypeptide (bovine PP) using the peroxidase antiperoxidase (PAP) method. Spherical to spindle shaped cells were demonstrated in the principal pancreatic islets in both species of teleost fishes. However, they were not detected in the exocrine portions nor the pancreatic ducts. Insulin-immunoreactive cells were located in the central regions of the principal pancreatic islets at high frequency in both species. Glucagonimmunoreactive cells were restricted to the peripheral regions of the principal pancreatic islets in both species. They formed a mantle zone in the peripheral regions of Silurus asotus with moderate frequency, and occupied a narrower mantle zone in Siniperca scherzeri with moderate frequency. In addition, glucagonimmunoreactive cell cores were also found in the peripheral zone of some principal pancreatic islets of Siniperca scherzeri. Somatostatin-immunoreactive cells were dispersed in the central zone of the principal pancreatic islets of Silurus asotus with moderate frequency, but were located in the peripheral regions with low frequency in Siniperca scherzeri. Bovine PPimmunoreactive cells were found in the peripheral region and the mantle zone of the principal pancreatic islets with low and rare frequency, respectively in both species. In conclusion, the regional distribution and relative frequency of endocrine cells in the principal pancreatic islets of Silurus asotus showed general patterns similar to those of other teleostean fishes. But, some speciesdependent distributional patterns and/or relative frequencies, particularly in glucagon-, somatostatin- and bovine PP-immunoreactive cells, were detected in the principal pancreatic islets of Siniperca scherzeri.

Immunohistochemical study on the distribution of endocrine cells in the gastrointestinal tract of the babirusa, Babyrousa babyrussa (Suidae).

The distribution and relative frequency of endocrine cells in the gastrointestinal tract of the babirusa were studied immunohistochemically using the avidin-biotin-peroxidase complex method. Thirteen types of gut endocrine cells were detected; they were immunoreactive for chromogranin, serotonin, somatostatin, gastrin, bovine pancreatic polypeptide (BPP), glucagon, secretin, cholecystokinin (CCK), methionine-enkephalin-Arg6-Gly7-Leu8 (MENK8), motilin, gastric inhibitory polypeptide (GIP) and peptide tyrosine tyrosine (PYY). Cells that were immunoreactive for chromogranin, serotonin, somatostatin and glucagon were found in all portions of the gastrointestinal tract. MENK8-immunoreactive cells were observed in the stomach and small intestine. Gastrin-immunoreactive cells were detected in the pyloric region and duodenum. PYY-immunoreactive cells were found in the small and large intestine. Cells immunoreactive for motilin, CCK, GIP, and secretin were observed in the proximal small intestine and those immunoreactive for neurotensin were found only in the ileum. Although the distribution pattern of endocrine cells in the gastrointestinal tract of babirusa was similar to those reported for pig, restricted distribution of several endocrine cells, gastrin, BPP, MENK8, motilin, CCK, GIP, secretin and neurotensin and wider distribution of glucagon and PYY were observed in the babirusa. The unexpected presence of MENK8 in all glandular regions of the stomach and PYY in the small intestine was also noted. The distribution of gut endocrine cells might be related to the regulatory characteristics of the babirusa digestive tract.

Immunohistochemistry of the pancreatic endocrine cells of the red‐eared slider(trachemys scripta elegans)

Regional distribution and relative frequency of endocrine cells in the pancreas of the red-eared slider, Trachemys scripta elegans, were investigated by immunohistochemical methods. Chromogranin (Cg) A-, serotonin-, insulin-, glucagon-, somatostatin-, bovine pancreatic polypeptide (BPP)- and human pancreatic polypeptede (HPP)-immunoreactive cells were identified in this study. Most of immunoreactive cells in the exocrine and endocrine pancreas (Langerhans islet) were generally spherical or spindle-shaped (open-typed cell), while occasionally cells round in shape (close-typed cell) were found in the basal portion or interepithelial regions of the pancreatic duct. These immunoreactive cells were located in the exocrine, endocrine pancreas and/or basal or interepithelial portion of the pancreatic duct. Serotonin-immunoreactive cells were found in the basal portion of epithelia of the pancreatic duct at a low frequency and interacinar region of the exocrine at a moderate frequency. Insulin-immunoreactive cells were found in the central portion of the endocrine pancreas, interacinar regions of the exocrine pancreas and basal portion of the epithelia of the pancreatic duct at high, moderate and low frequencies, respectively. Glucagon-immunoreactive cells were detected in the periphery of the endocrine pancreas, interacinar region of the exocrine pancreas and basal portion of the epithelia or interepithelia of the pancreatic duct at high, moderate and moderate frequencies, respectively. Somatostatin-immunoreactive cells were dispersed in the whole area of the endocrine pancreas, interacinar regions of exocrine pancreas and basal portion of the epithelia or interepithelia of the pancreatic duct at a moderate frequency. BPP- and HPP-immunoreactive cells were detected in the iinteracinar region of the exocrine pancreas at moderate and hige frequencies, respectively. However, no Cg A- and motilin-immunoreactive cells were detected in this study.

Immunocytochemical identification and localization of APUD cells in the gut of seven stomachless teleost fishes.

AIM:To study the cell types, localization, distribution density and morphology of APUD cells in the intestinal mucosa of stomachless teleost fishes.METHOD:By using the peroxidase antiperoxidase complex (PAP) immunocytochemical staining technique the identification, localization and morphology of immunoreactive (IR) endocrine cells seattered in the intestinal mucosa of grass carp (Cyenopharyngodon idellus), black carp ( Mylopharyngodon piceus ) and common carp (Cyprinus carpio) were investigated with 20 kinds of antisera prepared against mammalian peptide hormones of APUD cells, and likewise by using avidin-biotin-peroxidase complex (ABC) method those of silver carp (Hypophthalmichthys molitrix), bighead (Aristichthys nobilis), silver crucian carp (Carassius gibelio) and bluntnose black bream (Megalobrama amblyocephala ) were also studied with 5 different antisera. The replacement of the first antiserum by phosphate buffered saline (PBS) was employed as a control. IR endocrine cells were counted with a square-mesh ocular micrometer from 10 fields selected randomly in every section of each part of the intestine specimen. The average number of IR endocrine cells per mm(2) was counted to quantify their distribution density.RESULT:Gastrin (GAS), Gastric inhibitory peptide (GIP), glucagon (GLU), glucagons like immunorea-ctants (GLI), bovine pancreatic polypeptide (BPP), leucine-enkephalin (ENK) and substance P (SP)-IR endocrine cells were found in the gut of grass carp, black carp and common carp, and somatostatin (SOM) IR endocrine cells were only seen in common carp. GAS, GIP and GLU-IR endocrine cells were found in the intestinal mucosa of silver carp, bighead, silver crucian carp and bluntnose black bream. Most of IR endocrine cells had the higher distribution density in the foregut and midgut, and were longer in shape. They had a long apical cytoplasmic process extended to the gut lumen and a basal process extended to adjacent cells or basement membrane and touched with it. Sometimes, the basal cytoplasmic process formed an enlarged synapse-like structure in the contiguous part with basement membrane. This phenomenon provided new morpho-logical evidence for neuroendocrine and paracrine secretory function of these enteroendocrine cells.CONCLUTION:At least 8 kinds of IR endocrine cells were found in the gut of stomachless teleost species for the first time in China. These IR endocrine cells scattering in the gut mucosa belong to the APUD system. Among them, the hormones secreted by SP-, ENK-, SOM- and GLU-IR endocrine cells belong to the peptides of dual distribution in the brain and gut. This provided new evidence for the concept of brain-gut peptide. According to the cell types, distribution density, morphological characteristics and variety in shape of APUD cells in the gut of stomachless teleost fishes, it is deemed that the digestive tract of fishes is also an endocrine organ of great importance and complexity.

Immunocytochemistry of GABA in the central complex of the locust Schistocerca gregaria: identification of immunoreactive neurons and colocalization with neuropeptides.

The central complex is a highly organized neuropil structure in the insect brain and plays a role in motor control and visual orientation. We describe the distribution of gamma-aminobutyric acid (GABA) immunostaining in the central complex of the locust Schistocerca gregaria in an effort to analyze inhibitory neural circuits within this brain area. Antisera against GABA and the GABA-synthesizing enzyme glutamic acid decarboxylase resulted in identical patterns of immunostaining. Cell counts revealed about 100 bilateral pairs of GABA-immunoreactive neurons with arborizations in the central complex. Five types of immunostained neurons could be identified through reconstruction of the staining pattern, comparison with individually stained neurons, and double labeling experiments with Neurobiotin-injected neurons. All of these GABA-immunostained neurons are tangential neurons that connect the lateral accessory lobes to distinct layers of the central body. Three types of immunostained neurons (TL2, TL3, TL4) invade the lower division of the central body, and two additional types of neurons (TU1, TU2) have ramifications in layers I and II of the upper division of the central body. Double-labeling experiments with peptide antisera suggest that peptides related to Phe-Met-Arg-Phe-NH2/bovine pancreatic polypeptide and Dip-allatostatin might act as cotransmitters with GABA in TL4 neurons of the lower division and (Dip-allatostatin only) in TU2 neurons of the upper division of the central body. The high conservation in the pattern of GABA immunostaining in all insect species investigated so far suggests that GABA plays an essential role in the basic neural circuitry of the central complex in insects.

Immunohistochemical survey of the gut endocrine cells in the common tree shrew (Tupaia belangeri).

Regional distribution and relative frequency of endocrine cells in the gastrointestinal tract of the common tree shrew (Tupaia belangeri) were studied immunohistochemically. Ten types of immunoreactive endocrine cells were localized in the gastric mucosa, i.e., chromogranin-, serotonin-, gastrin-, somatostatin-, bovine pancreatic polypeptide (BPP)-, enteroglucagon-, pancreatic glucagon-, peptide tyrosine tyrosine (PYY)-, motilin-, and substance P (SP)-immunoreactive (IR) cells. In the intestine, 13 types of immunoreactive cells were observed, i.e., chromogranin-, serotonin-, somatostatin-, gastrin-, BPP-, enteroglucagon-, PYY-, secretin-, cholecystokinin (CCK)-, gastric inhibitory peptide (GIP)-, motilin-, neurotensin-, and SP-IR cells. The regional distribution and relative frequency of the cell types varied along the gastrointestinal tract. Basically, the types, distribution, and relative frequency of the gut endocrine cells were similar to those reported in other mammalian species. However, some characteristic findings were noted in the present study: (1) the considerably large number of gastrin-IR cells in the pyloric region; (2) numerous serotonin-IR cells in the stomach; (3) appreciable number of BPP-IR cells in the transitional region of the stomach; and (4) wide distribution of PYY- and motilin-IR cells in the gut.

Glucagon- and NPY-Related Peptide-Immunoreactive Cells in the Gut of Sea Bass (Dicentrarchus labraxL.): A Light and Electron Microscopic Study

Glucagon and peptide of the neuropeptide Y (NPY) family immunoreactivities were studied in the gut of sea bass (Dicentrarchus labrax) using antisera against bovine/porcine glucagon, porcine glucagon, glicentin (10–30), bovine pancreatic polypeptide (PP), peptide tyrosine tyrosine (PYY), salmon PYY (sPYY), and NPY. Glucagon-, glicentin-, PYY-, and NPY-immunoreactive (ir) cells were detected in the stomach, and glucagon-, PP-, PYY-, sPYY-, and NPY-ir cells in the intestine. PP, PYY, and NPY immunoreactivities coexisted in intestinal endocrine cells (NPY-like peptide containing cells), in some of which there was also glucagon immunoreactivity. Preabsorption tests indicated that different products of the glucagon gene(s) are probably expressed in the stomach and intestine of sea bass and that the peptides belonging to the NPY family in the endocrine cells of the intestine are more similar to NPY than to other peptides of this family. Glucagon-ir cells in the stomach, and glucagon/NPY-like containing cells in the intestine, were characterized by conventional and immunogold electron-microscopic techniques. The glucagon cells had secretory granules with a clotted content, the gold particles being observed in both the core and the halo. Glucagon/NPY-like cells showed two types of secretory granules differing in size, both of which were immunogold labeled with anti-NPY and anti-sPYY; the smaller granules were weakly immunogold labeled with anti-glucagon.